A field trip to determine the work capacity of high altitude natives (14,850 ft) suffering from Monge's disease before and after phlebotomy. Using a computer controlled exercise stress test, several high altitude natives were tested before and after massive phlebotomy. Enough red cells were removed and replaced with albumin to lower their hemocrit to 50-52%. This usually meant that three liters of red cells were removed. In all cases, the improvement in performance was dramatic ranging from 50%-150% increase in work output.